期刊
MOLECULAR AND CELLULAR BIOLOGY
卷 30, 期 20, 页码 4952-4964出版社
AMER SOC MICROBIOLOGY
DOI: 10.1128/MCB.00299-10
关键词
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资金
- Japan Science and Technology Agency
- Special Coordination Funds for Promoting Science and Technology
- Ministry of Education, Culture, Sports, Science, and Technology of Japan [19038003, 20052005, 21113005, 17013018]
- RIKEN
- Ichiro Kanehara Foundation
- Grants-in-Aid for Scientific Research [17013018, 22570132, 20052005, 19038003, 21113005] Funding Source: KAKEN
Histone chaperones regulate the density of incorporated histone proteins around DNA transcription sites and therefore constitute an important site-specific regulatory mechanism for the control of gene expression. At present, the targeting mechanism conferring this site specificity is unknown. We previously reported that the histone chaperone B23/nucleophosmin associates with rRNA chromatin (r-chromatin) to stimulate rRNA transcription. Here, we report on the mechanism for site-specific targeting of B23 to the r-chromatin. We observed that, during mitosis, B23 was released from chromatin upon inactivation of its RNA binding activity by cdc2 kinase-mediated phosphorylation. The phosphorylation status of B23 was also shown to strongly affect its chromatin binding activity. We further found that r-chromatin binding of B23 was a necessary condition for B23 histone chaperone activity in vivo. In addition, we found that depletion of upstream binding factor (UBF; an rRNA transcription factor) decreased the chromatin binding affinity of B23, which in turn led to an increase in histone density at the r-chromatin. These two major strands of evidence suggest a novel cell cycle-dependent mechanism for the site-specific regulation of histone density via joint RNA-and transcription factor-mediated recruitment of histone chaperones to specific chromosome loci.
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